VRAMs and DRAMS, are well-known in the art. Typically, VRAMs incorporate more circuitry, like SAMs, to enable faster memory speeds which are required by video imaging processes. However, DRAMs have had a small market in the video arena. Specifically, when customers do not require the faster access speeds, a DRAM has adequate speeds and is less expensive to use.
One particular use for a VRAM, is to perform a "row copy" operation. This operation is used when there's a solid block area on a video screen that requires a repetition of information. For example, most people will be familiar with background images in word processing screen displays. Where the screen is all green or blue, and the operator types over in another color for the text. The solid block area is created by a row copy operation. Where each bit of memory information is the same for each column and row in the memory array assigned to that block of color.